The present invention relates to a data storage apparatus, and in particular it relates to magnetic head retraction for a rotary actuator type magnetic disk apparatus.
Various methods have been proposed for moving a magnetic head to a non-data recorded portion of a disk, for example to a shipping region on a magnetic recording disk, and for securing the same at that position when the magnetic recording disk in a magnetic disk apparatus stops its rotation.
When a magnetic recording disk is rotating and a magnetic head is conducting data read/write operation, the magnetic head is not usually in direct contact with the magnetic recording disk but floats slightly above the surface of the disk due to an air stream bearing caused by rotation of the disk. However, when the magnetic recording disk stops its rotation, the air stream disappears and the magnetic head comes into contact with the magnetic recording disk. If this contact happens in a data area, recorded data may be destroyed. Therefore, whenever the magnetic recording disk stops its rotation, the magnetic head should be moved to the shipping or non-data recorded region and secured at that position, that it should undergo a retracting operation.
Japanese Patent Laid-open Nos. 269275/1986 and 86982/1991 relate to the force of a coil spring and a leaf spring, respectively, applied in one direction to an actuator to cause the magnetic head to be moved to a predetermined position on the magnetic recording disk. These devices require valuable space for installation and increase the number of components. The coil spring produces oscillation of the head when it should be at rest, which will produce a lot of harmful debris and may eventually break the spring. The leaf spring has a short life span due to repeated bending over a wide range.
Further, for securing the magnetic head in the shipping region, Japanese Patent Laid-open No. 245579/1987 secures the actuator in the shipping region by magnetic attraction using a special-purpose permanent magnet, which can deteriorate over time to change the accuracy of movement by the VCM and which increases space requirements and complexity due to its location and mounting hardware. Also bias is only effective after the head reaches the shipping region, not throughout the range movement. Further, a permanent magnet is not desirable because oxidation occurs and produces harmful oxide dust. Reliability is bad because changes in polarity can occur due to high intensity leakage flux from the VCM.